1. Field of the Invention
This invention relates generally to semiconductor manufacturing, and, more particularly, to a method and apparatus for updating a process controller based upon a fault detection analysis.
2. Description of the Related Art
The technology explosion in the manufacturing industry has resulted in many new and innovative manufacturing processes. Today's manufacturing processes, particularly semiconductor manufacturing processes, call for a large number of important steps. These process steps are usually vital, and therefore, require a number of inputs that are generally fine-tuned to maintain proper manufacturing control.
The manufacture of semiconductor devices requires a number of discrete process steps to create a packaged semiconductor device from raw semiconductor material. The various processes, from the initial growth of the semiconductor material, the slicing of the semiconductor crystal into individual wafers, the fabrication stages (etching, doping, ion implanting, or the like), to the packaging and final testing of the completed device, are so different from one another and specialized that the processes may be performed in different manufacturing locations that contain different control schemes.
Generally, a set of processing steps is performed across a group of semiconductor wafers, sometimes referred to as a lot. For example, a process layer that may be composed of a variety of different materials may be formed across a semiconductor wafer. Thereafter, a patterned layer of photoresist may be formed across the process layer using known photolithography techniques. Typically, an etch process is then performed across the process layer using the patterned layer of photoresist as a mask. This etching process results in the formation of various features or objects in the process layer. Such features may be used as, for example, a gate electrode structure for transistors. Many times, trench isolation structures are also formed across the substrate of the semiconductor wafer to isolate electrical areas across a semiconductor wafer. One example of an isolation structure that can be used is a shallow trench isolation (STI) structure.
The manufacturing tools within a semiconductor manufacturing facility typically communicate with a manufacturing framework or a network of processing modules. Each manufacturing tool is generally connected to an equipment interface. The equipment interface is connected to a machine interface to which a manufacturing network is connected, thereby facilitating communications between the manufacturing tool and the manufacturing framework. The machine interface can generally be part of an advanced process control (APC) system. The APC system initiates a control script, which can be a software program that automatically retrieves the data needed to execute a manufacturing process.
FIG. 1 illustrates a typical semiconductor wafer 105. The semiconductor wafer 105 typically includes a plurality of individual semiconductor die 103 arranged in a grid 150. Using known photolithography processes and equipment, a patterned layer of photoresist may be formed across one or more process layers that are to be patterned. As part of the photolithography process, an exposure process is typically performed by a stepper on approximately one to four die 103 locations at a time, depending on the specific photomask employed. The patterned photoresist layer can be used as a mask during etching processes, wet or dry, performed on the underlying layer or layers of material, e.g., a layer of polysilicon, metal or insulating material, to transfer the desired pattern to the underlying layer. The patterned layer of photoresist is comprised of a plurality of features, e.g., line-type features or opening-type features that are to be replicated in an underlying process layer.
The health of a processing tool (tool health) may vary over time. The tool health may relate to an assessment of how well the processing tool operates within a predetermined specification, which may include specifications such as tool environment characteristics (e.g., tool temperature, humidity, and the like) and quality and accuracy of the process performed by the processing tool. Variations in the tool health may occur and adversely affect the quality of processed semiconductor wafers 105. Variations in the tool health may cause degradation in the operation of a processing tool.
Turning now to FIG. 2, a typical flow of processes performed on a semiconductor wafer 105 by a semiconductor manufacturing system is illustrated. A manufacturing system processes semiconductor wafers 105 (block 210). Upon processing of the semiconductor wafers 105, the manufacturing system may acquire metrology data relating to the processed semiconductor wafers 105 (block 220). The manufacturing system may then perform an analysis upon the acquired metrology data (block 230). In response to the analysis of the metrology data, the manufacturing system may calculate corrections that may be made to the process control (block 240). The manufacturing system may then implement the calculated corrections upon the process control, such as by using a feedback correction (block 250).
The manufacturing system may also acquire tool state data relating to processing of the semiconductor wafers 105 (block 270). Generally, an analysis of the acquired tool state data is then performed (block 280). The tool state data may include data, such as pressure data, temperature data, humidity data, gas flow rate data, and other manufacturing type data. Based upon the tool state data, the manufacturing system may determine the tool health (block 290). The manufacturing system then determines whether the tool health is adequate to continue processing (block 295). Upon a determination that the tool health is not adequate to continue processing, the manufacturing system may then stop processing semiconductor wafers 105 (block 297). When the manufacturing system determines that the tool health is adequate to continue processing, manufacturing of the semiconductor wafers 105 is continued (block 260).
One problem associated with the current methodology is that the metrology data may be adversely affected by a decline in the tool health. In other words, the metrology data may not accurately reflect the actual accuracy of the parameters used to process the semiconductor wafers 105. Therefore, when a processing tool experiences a decline in the tool health, metrology data is affected and an incorrect amount of compensation or correction that otherwise would not have been applied, may be implemented as a result. This may lead to excessive corrections that may not provide accurately processed wafers.
Furthermore, a significant control modification may be implemented, which may affect the metrology data. However, the resultant change in metrology data combined with the analysis performed on the tool state data may cause the manufacturing system to interpret that a decline in the tool health has taken place; even though the tool state data may be reflecting a substantial change in the process control. This will result in misdiagnoses of the tool health, which may result in mis-processing of semiconductor wafers 105.
The present invention is directed to overcoming, or at least reducing, the effects of, one or more of the problems set forth above.